¹³C NMR study of the enol forms of β‐diketones

Abstract

Abstract Carbon‐13 NMR spectra of a series of β‐diketones in the enol form with various β‐substituents have been studied. An additive influence of the β‐substituents on the chemical shifts of the carbon atoms in the hydrogen bonded chelate ring has been found. It is shown that the α‐ and β‐carbon chemical shifts can be calculated by means of a set of increments for arbitrary combinations of the X and Y substituents. Analysis of the experimental data enables the conclusions to be drawn that enol–enolic tautomerism with different populations of the forms (A) and (B) is absent in β‐diketones and that the carbon chemical shift changes are caused by electron density redistribution in the hydrogen bonded chelate ring (C).